Aphyocharax anisitsi

The Bloodfin Tetra, scientifically known as Aphyocharax anisitsi, is a robust and dynamic characin originating from the river basins of South America. Its resilience makes it exceptionally well-suited for a wide range of community tank setups. For optimal health, a tank of at least 60 liters is recommended to provide adequate swimming space for a proper school. These fish thrive in water with a moderate current, which mimics the flowing streams of their natural habitat and encourages their active swimming behavior. One of their most valued traits is their adaptability to diverse water chemistry, tolerating a broad pH spectrum from 6.0 to 8.0 and a wide range of water hardness levels. This makes them compatible with tap water in many regions without extensive modification.

In terms of aquascape, provide plenty of open space in the middle and top water columns where they predominantly swim. Planting the background and sides heavily with plants like Vallisneria or Hornwort will offer them security and places to retreat. As omnivores, their diet should be varied. A high-quality flake or micro-pellet food can serve as a staple, but it should be supplemented regularly with frozen or live foods such as brine shrimp, daphnia, and bloodworms. This not only provides essential nutrients but also promotes natural foraging behaviors and enhances the vibrancy of their red fins.

Socially, the Bloodfin Tetra is a quintessential schooling fish. A group of six is the absolute minimum, but a larger school of ten or more is highly recommended. In a larger group, their shoaling behavior becomes more pronounced, and any potential for fin-nipping is dispersed amongst the group rather than focused on tank mates. Their 'triggered_by_long_fins' trait means they are poor companions for slow-moving, long-finned species like Bettas, Guppies, or Angelfish. Instead, they cohabitate well with other fast-moving fish of similar size, such as other tetras, danios, rasboras, and bottom-dwelling Corydoras catfish. Breeding is achievable for the dedicated hobbyist; they are egg-scatterers that require a separate breeding tank with fine-leaved plants or a spawning mop, as the parents will consume their own eggs if not removed post-spawning.

Aphyocharax anisitsi, a member of the Characidae family, is a small, freshwater teleost native to the Paraná and Uruguay River basins in South America. Its classification within the order Characiformes places it among a diverse group of fish known for their active, often shoaling behaviors.

Morphology & Anatomy: The species exhibits a fusiform body shape, an adaptation for efficient locomotion in habitats with moderate water flow. The body is laterally compressed with silvery, iridescent scales that reflect light. The key diagnostic feature is the intense red to orange pigmentation on the caudal, dorsal, anal, and adipose fins, which contrasts sharply with the hyaline nature of the pectoral fins. This coloration serves as a visual cue for species recognition and shoaling cohesion. Adult specimens typically reach a standard length of 4 to 6 centimeters.

Ecological Niche & Habitat Parameters: In its natural environment, A. anisitsi inhabits clear, freshwater streams and tributaries. Its physiological adaptability is notable, allowing it to thrive across a broad range of physicochemical water parameters. It tolerates a pH range of 6.0 to 8.0 and a wide range of general hardness, from approximately 2 to 15 dGH (corresponding to 36-268 ppm). This demonstrates significant osmoregulatory capacity. The species is stenohaline, with a maximum salinity tolerance of only 0.5 ppt. Its diet is omnivorous, consisting of small invertebrates, crustaceans, algae, and benthic detritus in the wild.

Physiology and In-Aquaria Biology: A. anisitsi has a medium metabolic rate coupled with low oxygen consumption, indicating efficient aerobic respiration suited to its constantly active state. The calculated bioload factor of 1.6 suggests a moderate impact on the nitrogen cycle within a closed aquatic system, producing a relatively low amount of organic waste for its size and activity level. This physiological efficiency contributes to its reputation as a hardy species in captivity. Behaviorally, it is an obligate-schooling fish, requiring conspecifics to mitigate stress and exhibit natural pelagic behaviors, primarily occupying the top and middle strata of the water column. Its IUCN status is currently Not Evaluated (NE), indicating a lack of formal assessment of its wild population's conservation status.